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root/jsr166/jsr166/src/jsr166y/Phaser.java

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.49 by dl, Fri Nov 5 23:01:47 2010 UTC vs.
Revision 1.52 by dl, Sat Nov 13 01:27:13 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11		import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
#	Line 226 | Line 227 | public class Phaser {
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229		*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236		* packed into a single (atomic) long. Termination uses the sign
237		* bit of 32 bit representation of phase, so phase is set to -1 on
238		* termination. Good performance relies on keeping state decoding
239		* and encoding simple, and keeping race windows short.
239	–	*
240	–	* Note: there are some cheats in arrive() that rely on unarrived
241	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortMask = 0xffff;
244	<	private static final int phaseMask  = 0x7fffffff;
243	>	private static final int  MAX_COUNT      = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final long UNARRIVED_MASK = 0xffffL;
248	>	private static final long PARTIES_MASK   = 0xffff0000L;
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int) (s & ushortMask);
256	>	return (int) (s & UNARRIVED_MASK);
257		}
258
259		private static int partiesOf(long s) {
260	<	return ((int) s) >>> 16;
260	>	return ((int) (s & PARTIES_MASK)) >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int) (s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
264	–	private static long stateFor(int phase, int parties, int unarrived) {
265	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
266	–	(long) unarrived);
267	–	}
268	–
269	–	private static long trippedStateFor(int phase, int parties) {
270	–	long lp = (long) parties;
271	–	return (((long) phase) << 32) | (lp << 16) | lp;
272	–	}
273	–
274	–	/**
275	–	* Returns message string for bad bounds exceptions.
276	–	*/
277	–	private static String badBounds(int parties, int unarrived) {
278	–	return ("Attempt to set " + unarrived +
279	–	" unarrived of " + parties + " parties");
280	–	}
281	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
#	Line 290 | Line 279 | public class Phaser {
279		*/
280		private final Phaser root;
281
293	–	// Wait queues
294	–
282		/**
283		* Heads of Treiber stacks for waiting threads. To eliminate
284		* contention when releasing some threads while adding others, we
285		* use two of them, alternating across even and odd phases.
286		* Subphasers share queues with root to speed up releases.
287		*/
288	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
289	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
288	>	private final AtomicReference<QNode> evenQ;
289	>	private final AtomicReference<QNode> oddQ;
290
291		private AtomicReference<QNode> queueFor(int phase) {
292	<	Phaser r = root;
293	<	return ((phase & 1) == 0) ? r.evenQ : r.oddQ;
292	>	return ((phase & 1) == 0) ? evenQ : oddQ;
293	>	}
294	>
295	>	/**
296	>	* Main implementation for methods arrive and arriveAndDeregister.
297	>	* Manually tuned to speed up and minimize race windows for the
298	>	* common case of just decrementing unarrived field.
299	>	*
300	>	* @param adj - adjustment to apply to state -- either
301	>	* ONE_ARRIVAL (for arrive) or
302	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
303	>	*/
304	>	private int doArrive(long adj) {
305	>	long s;
306	>	int phase, unarrived;
307	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
308	>	if ((unarrived = (int)(s & UNARRIVED_MASK)) != 0) {
309	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)) {
310	>	if (unarrived == 1) {
311	>	Phaser par;
312	>	long p = s & PARTIES_MASK; // unshifted parties field
313	>	long lu = p >>> PARTIES_SHIFT;
314	>	int u = (int)lu;
315	>	int nextPhase = (phase + 1) & MAX_PHASE;
316	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
317	>	if ((par = parent) == null) {
318	>	UNSAFE.compareAndSwapLong
319	>	(this, stateOffset, s, onAdvance(phase, u)?
320	>	next | TERMINATION_PHASE : next);
321	>	releaseWaiters(phase);
322	>	}
323	>	else {
324	>	par.doArrive(u == 0?
325	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
326	>	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
327	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
328	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
329	>	s, next)))
330	>	reconcileState();
331	>	}
332	>	}
333	>	break;
334	>	}
335	>	}
336	>	else if (state == s && reconcileState() == s) // recheck
337	>	throw new IllegalStateException(badArrive());
338	>	}
339	>	return phase;
340		}
341
342		/**
343	<	* Returns current state, first resolving lagged propagation from
344	<	* root if necessary.
343	>	* Returns message string for bounds exceptions on arrival.
344	>	* Declared out of-line from doArrive to reduce string op bulk.
345		*/
346	<	private long getReconciledState() {
347	<	return (parent == null) ? state : reconcileState();
346	>	private String badArrive() {
347	>	return ("Attempted arrival of unregistered party for " +
348	>	this.toString());
349		}
350
351		/**
352	<	* Recursively resolves state.
352	>	* Implementation of register, bulkRegister
353	>	*
354	>	* @param registrations number to add to both parties and unarrived fields
355	>	*/
356	>	private int doRegister(int registrations) {
357	>	long adj = (long)registrations; // adjustment to state
358	>	adj |= adj << PARTIES_SHIFT;
359	>	Phaser par = parent;
360	>	long s;
361	>	int phase;
362	>	while ((phase = (int)((s = (par == null? state : reconcileState()))
363	>	>>> PHASE_SHIFT)) >= 0) {
364	>	int parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT;
365	>	if (parties != 0 && (s & UNARRIVED_MASK) == 0)
366	>	internalAwaitAdvance(phase, null); // wait for onAdvance
367	>	else if (parties + registrations > MAX_COUNT)
368	>	throw new IllegalStateException(badRegister());
369	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
370	>	break;
371	>	}
372	>	return phase;
373	>	}
374	>
375	>	/**
376	>	* Returns message string for bounds exceptions on registration
377	>	*/
378	>	private String badRegister() {
379	>	return ("Attempt to register more than " + MAX_COUNT + " parties for "+
380	>	this.toString());
381	>	}
382	>
383	>	/**
384	>	* Recursively resolves lagged phase propagation from root if
385	>	* necessary.
386		*/
387		private long reconcileState() {
388		Phaser par = parent;
389	<	long s = state;
390	<	if (par != null) {
391	<	int phase, rootPhase;
392	<	while ((phase = phaseOf(s)) >= 0 &&
393	<	(rootPhase = phaseOf(root.state)) != phase &&
394	<	(rootPhase < 0 || unarrivedOf(s) == 0)) {
395	<	long parentState = par.getReconciledState();
396	<	int parentPhase = phaseOf(parentState);
397	<	int parties = partiesOf(s);
398	<	long next = trippedStateFor(parentPhase, parties);
399	<	if (phaseOf(root.state) == rootPhase &&
400	<	parentPhase != phase &&
401	<	state == s && casState(s, next)) {
402	<	releaseWaiters(phase);
403	<	if (parties == 0) // exit if the final deregistration
404	<	break;
389	>	if (par == null)
390	>	return state;
391	>	Phaser rt = root;
392	>	long s;
393	>	int phase, rPhase;
394	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0 &&
395	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
396	>	if (rPhase < 0 || (s & UNARRIVED_MASK) == 0) {
397	>	long ps = par.parent == null? par.state : par.reconcileState();
398	>	int pPhase = (int)(ps >>> PHASE_SHIFT);
399	>	if (pPhase < 0 || pPhase == ((phase + 1) & MAX_PHASE)) {
400	>	if (state != s)
401	>	continue;
402	>	long p = s & PARTIES_MASK;
403	>	long next = ((((long) pPhase) << PHASE_SHIFT) |
404	>	(p >>> PARTIES_SHIFT) | p);
405	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
406	>	return next;
407		}
339	–	s = state;
408		}
409	+	if (state == s)
410	+	releaseWaiters(phase); // help release others
411		}
412		return s;
413		}
#	Line 348 | Line 418 | public class Phaser {
418		* phaser will need to first register for it.
419		*/
420		public Phaser() {
421	<	this(null);
421	>	this(null, 0);
422		}
423
424		/**
#	Line 372 | Line 442 | public class Phaser {
442		* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
376	<	this.parent = parent;
377	<	if (parent != null) {
378	<	this.root = parent.root;
379	<	phase = parent.register();
380	<	}
381	<	else
382	<	this.root = this;
383	<	this.state = trippedStateFor(phase, 0);
445	>	this(parent, 0);
446		}
447
448		/**
#	Line 395 | Line 457 | public class Phaser {
457		* or greater than the maximum number of parties supported
458		*/
459		public Phaser(Phaser parent, int parties) {
460	<	if (parties < 0 || parties > ushortMask)
460	>	if (parties < 0 || parties > MAX_COUNT)
461		throw new IllegalArgumentException("Illegal number of parties");
462	<	int phase = 0;
462	>	int phase;
463		this.parent = parent;
464		if (parent != null) {
465	<	this.root = parent.root;
465	>	Phaser r = parent.root;
466	>	this.root = r;
467	>	this.evenQ = r.evenQ;
468	>	this.oddQ = r.oddQ;
469		phase = parent.register();
470		}
471	<	else
471	>	else {
472		this.root = this;
473	<	this.state = trippedStateFor(phase, parties);
473	>	this.evenQ = new AtomicReference<QNode>();
474	>	this.oddQ = new AtomicReference<QNode>();
475	>	phase = 0;
476	>	}
477	>	long p = (long)parties;
478	>	this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
479		}
480
481		/**
482		* Adds a new unarrived party to this phaser.
483		* If an ongoing invocation of {@link #onAdvance} is in progress,
484	<	* this method waits until its completion before registering.
484	>	* this method may wait until its completion before registering.
485		*
486		* @return the arrival phase number to which this registration applied
487		* @throws IllegalStateException if attempting to register more
#	Line 424 | Line 494 | public class Phaser {
494		/**
495		* Adds the given number of new unarrived parties to this phaser.
496		* If an ongoing invocation of {@link #onAdvance} is in progress,
497	<	* this method waits until its completion before registering.
497	>	* this method may wait until its completion before registering.
498		*
499		* @param parties the number of additional parties required to trip barrier
500		* @return the arrival phase number to which this registration applied
#	Line 435 | Line 505 | public class Phaser {
505		public int bulkRegister(int parties) {
506		if (parties < 0)
507		throw new IllegalArgumentException();
508	+	if (parties > MAX_COUNT)
509	+	throw new IllegalStateException(badRegister());
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
444	–	* Shared code for register, bulkRegister
445	–	*/
446	–	private int doRegister(int registrations) {
447	–	Phaser par = parent;
448	–	long s;
449	–	int phase;
450	–	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
451	–	int p = partiesOf(s);
452	–	int u = unarrivedOf(s);
453	–	int unarrived = u + registrations;
454	–	int parties = p + registrations;
455	–	if (par == null || phase == phaseOf(root.state)) {
456	–	if (parties > ushortMask || unarrived > ushortMask)
457	–	throw new IllegalStateException(badBounds(parties,
458	–	unarrived));
459	–	else if (p != 0 && u == 0)       // back off if advancing
460	–	Thread.yield();              // not worth actually blocking
461	–	else if (casState(s, stateFor(phase, parties, unarrived)))
462	–	break;
463	–	}
464	–	}
465	–	return phase;
466	–	}
467	–
468	–	/**
516		* Arrives at the barrier, but does not wait for others.  (You can
517		* in turn wait for others via {@link #awaitAdvance}).  It is an
518		* unenforced usage error for an unregistered party to invoke this
#	Line 476 | Line 523 | public class Phaser {
523		* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	Phaser par = parent;
480	<	long s;
481	<	int phase;
482	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
483	<	int parties = partiesOf(s);
484	<	int unarrived = unarrivedOf(s) - 1;
485	<	if (parties == 0 || unarrived < 0)
486	<	throw new IllegalStateException(badBounds(parties,
487	<	unarrived));
488	<	else if (unarrived > 0) {           // Not the last arrival
489	<	if (casState(s, s - 1))         // s-1 adds one arrival
490	<	break;
491	<	}
492	<	else if (par == null) {             // directly trip
493	<	if (casState(s, trippedStateFor(onAdvance(phase, parties) ? -1 :
494	<	((phase + 1) & phaseMask),
495	<	parties))) {
496	<	releaseWaiters(phase);
497	<	break;
498	<	}
499	<	}
500	<	else if (phaseOf(root.state) == phase && casState(s, s - 1)) {
501	<	par.arrive();                   // cascade to parent
502	<	reconcileState();
503	<	break;
504	<	}
505	<	}
506	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
#	Line 520 | Line 540 | public class Phaser {
540		* of registered or unarrived parties would become negative
541		*/
542		public int arriveAndDeregister() {
543	<	// similar to arrive, but too different to merge
524	<	Phaser par = parent;
525	<	long s;
526	<	int phase;
527	<	while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) {
528	<	int parties = partiesOf(s) - 1;
529	<	int unarrived = unarrivedOf(s) - 1;
530	<	if (parties < 0 || unarrived < 0)
531	<	throw new IllegalStateException(badBounds(parties,
532	<	unarrived));
533	<	else if (unarrived > 0) {
534	<	if (casState(s, stateFor(phase, parties, unarrived)))
535	<	break;
536	<	}
537	<	else if (par == null) {
538	<	if (casState(s, trippedStateFor(onAdvance(phase, parties)? -1:
539	<	(phase + 1) & phaseMask,
540	<	parties))) {
541	<	releaseWaiters(phase);
542	<	break;
543	<	}
544	<	}
545	<	else if (phaseOf(root.state) == phase &&
546	<	casState(s, stateFor(phase, parties, 0))) {
547	<	if (parties == 0)
548	<	par.arriveAndDeregister();
549	<	else
550	<	par.arrive();
551	<	reconcileState();
552	<	break;
553	<	}
554	<	}
555	<	return phase;
543	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
544		}
545
546		/**
#	Line 576 | Line 564 | public class Phaser {
564		* Awaits the phase of the barrier to advance from the given phase
565		* value, returning immediately if the current phase of the
566		* barrier is not equal to the given phase value or this barrier
567	<	* is terminated.  It is an unenforced usage error for an
580	<	* unregistered party to invoke this method.
567	>	* is terminated.
568		*
569		* @param phase an arrival phase number, or negative value if
570		* terminated; this argument is normally the value returned by a
#	Line 588 | Line 575 | public class Phaser {
575		public int awaitAdvance(int phase) {
576		if (phase < 0)
577		return phase;
578	<	int p = getPhase();
578	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
579		if (p != phase)
580		return p;
581	<	return untimedWait(phase);
581	>	return internalAwaitAdvance(phase, null);
582		}
583
584		/**
#	Line 599 | Line 586 | public class Phaser {
586		* value, throwing {@code InterruptedException} if interrupted
587		* while waiting, or returning immediately if the current phase of
588		* the barrier is not equal to the given phase value or this
589	<	* barrier is terminated. It is an unenforced usage error for an
603	<	* unregistered party to invoke this method.
589	>	* barrier is terminated.
590		*
591		* @param phase an arrival phase number, or negative value if
592		* terminated; this argument is normally the value returned by a
#	Line 613 | Line 599 | public class Phaser {
599		throws InterruptedException {
600		if (phase < 0)
601		return phase;
602	<	int p = getPhase();
602	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
603		if (p != phase)
604		return p;
605	<	return interruptibleWait(phase);
605	>	QNode node = new QNode(this, phase, true, false, 0L);
606	>	p = internalAwaitAdvance(phase, node);
607	>	if (node.wasInterrupted)
608	>	throw new InterruptedException();
609	>	else
610	>	return p;
611		}
612
613		/**
#	Line 625 | Line 616 | public class Phaser {
616		* InterruptedException} if interrupted while waiting, or
617		* returning immediately if the current phase of the barrier is
618		* not equal to the given phase value or this barrier is
619	<	* terminated.  It is an unenforced usage error for an
629	<	* unregistered party to invoke this method.
619	>	* terminated.
620		*
621		* @param phase an arrival phase number, or negative value if
622		* terminated; this argument is normally the value returned by a
#	Line 646 | Line 636 | public class Phaser {
636		long nanos = unit.toNanos(timeout);
637		if (phase < 0)
638		return phase;
639	<	int p = getPhase();
639	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
640		if (p != phase)
641		return p;
642	<	return timedWait(phase, nanos);
642	>	QNode node = new QNode(this, phase, true, true, nanos);
643	>	p = internalAwaitAdvance(phase, node);
644	>	if (node.wasInterrupted)
645	>	throw new InterruptedException();
646	>	else if (p == phase)
647	>	throw new TimeoutException();
648	>	else
649	>	return p;
650		}
651
652		/**
#	Line 662 | Line 659 | public class Phaser {
659		public void forceTermination() {
660		Phaser r = root;    // force at root then reconcile
661		long s;
662	<	while (phaseOf(s = r.state) >= 0)
663	<	r.casState(s, stateFor(-1, partiesOf(s), unarrivedOf(s)));
662	>	while ((s = r.state) >= 0)
663	>	UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE);
664		reconcileState();
665	<	releaseWaiters(0);  // ensure wakeups on both queues
665	>	releaseWaiters(0); // signal all threads
666		releaseWaiters(1);
667		}
668
#	Line 677 | Line 674 | public class Phaser {
674		* @return the phase number, or a negative value if terminated
675		*/
676		public final int getPhase() {
677	<	return phaseOf(getReconciledState());
677	>	return (int)((parent == null? state : reconcileState()) >>> PHASE_SHIFT);
678		}
679
680		/**
#	Line 686 | Line 683 | public class Phaser {
683		* @return the number of parties
684		*/
685		public int getRegisteredParties() {
686	<	return partiesOf(getReconciledState());
686	>	return partiesOf(parent == null? state : reconcileState());
687		}
688
689		/**
#	Line 696 | Line 693 | public class Phaser {
693		* @return the number of arrived parties
694		*/
695		public int getArrivedParties() {
696	<	return arrivedOf(getReconciledState());
696	>	return arrivedOf(parent == null? state : reconcileState());
697		}
698
699		/**
#	Line 706 | Line 703 | public class Phaser {
703		* @return the number of unarrived parties
704		*/
705		public int getUnarrivedParties() {
706	<	return unarrivedOf(getReconciledState());
706	>	return unarrivedOf(parent == null? state : reconcileState());
707		}
708
709		/**
#	Line 734 | Line 731 | public class Phaser {
731		* @return {@code true} if this barrier has been terminated
732		*/
733		public boolean isTerminated() {
734	<	return getPhase() < 0;
734	>	return (parent == null? state : reconcileState()) < 0;
735		}
736
737		/**
#	Line 750 | Line 747 | public class Phaser {
747		* which case no advance occurs.
748		*
749		* <p>The arguments to this method provide the state of the phaser
750	<	* prevailing for the current transition. (When called from within
751	<	* an implementation of {@code onAdvance} the values returned by
752	<	* methods such as {@code getPhase} may or may not reliably
753	<	* indicate the state to which this transition applies.)
750	>	* prevailing for the current transition.  The effects of invoking
751	>	* arrival, registration, and waiting methods on this Phaser from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on.
754	>	*
755	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
756	>	* {@code onAdvance} is invoked only for its root Phaser on each
757	>	* advance.
758		*
759		* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
#	Line 778 | Line 779 | public class Phaser {
779		* @return a string identifying this barrier, as well as its state
780		*/
781		public String toString() {
782	<	long s = getReconciledState();
782	>	long s = reconcileState();
783		return super.toString() +
784		"[phase = " + phaseOf(s) +
785		" parties = " + partiesOf(s) +
786		" arrived = " + arrivedOf(s) + "]";
787		}
788
789	<	// methods for waiting
789	>	/**
790	>	* Removes and signals threads from queue for phase
791	>	*/
792	>	private void releaseWaiters(int phase) {
793	>	AtomicReference<QNode> head = queueFor(phase);
794	>	QNode q;
795	>	int p;
796	>	while ((q = head.get()) != null &&
797	>	((p = q.phase) == phase ||
798	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
799	>	if (head.compareAndSet(q, q.next))
800	>	q.signal();
801	>	}
802	>	}
803	>
804	>	/**
805	>	* Tries to enqueue given node in the appropriate wait queue.
806	>	*
807	>	* @return true if successful
808	>	*/
809	>	private boolean tryEnqueue(int phase, QNode node) {
810	>	releaseWaiters(phase-1); // ensure old queue clean
811	>	AtomicReference<QNode> head = queueFor(phase);
812	>	QNode q = head.get();
813	>	return ((q == null || q.phase == phase) &&
814	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
815	>	head.compareAndSet(node.next = q, node));
816	>	}
817	>
818	>	/** The number of CPUs, for spin control */
819	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
820	>
821	>	/**
822	>	* The number of times to spin before blocking while waiting for
823	>	* advance, per arrival while waiting. On multiprocessors, fully
824	>	* blocking and waking up a large number of threads all at once is
825	>	* usually a very slow process, so we use rechargeable spins to
826	>	* avoid it when threads regularly arrive: When a thread in
827	>	* internalAwaitAdvance notices another arrival before blocking,
828	>	* and there appear to be enough CPUs available, it spins
829	>	* SPINS_PER_ARRIVAL more times before continuing to try to
830	>	* block. The value trades off good-citizenship vs big unnecessary
831	>	* slowdowns.
832	>	*/
833	>	static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8;
834	>
835	>	/**
836	>	* Possibly blocks and waits for phase to advance unless aborted.
837	>	*
838	>	* @param phase current phase
839	>	* @param node if nonnull, the wait node to track interrupt and timeout;
840	>	* if null, denotes noninterruptible wait
841	>	* @return current phase
842	>	*/
843	>	private int internalAwaitAdvance(int phase, QNode node) {
844	>	Phaser current = this;       // to eventually wait at root if tiered
845	>	Phaser par = parent;
846	>	boolean queued = false;
847	>	int spins = SPINS_PER_ARRIVAL;
848	>	int lastUnarrived = -1;      // to increase spins upon change
849	>	long s;
850	>	int p;
851	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
852	>	int unarrived = (int)(s & UNARRIVED_MASK);
853	>	if (unarrived != lastUnarrived) {
854	>	if ((lastUnarrived = unarrived) < NCPU)
855	>	spins += SPINS_PER_ARRIVAL;
856	>	}
857	>	else if (unarrived == 0 && par != null) {
858	>	current = par;       // if all arrived, use parent
859	>	par = par.parent;
860	>	}
861	>	else if (spins > 0)
862	>	--spins;
863	>	else if (node == null)
864	>	node = new QNode(this, phase, false, false, 0L);
865	>	else if (node.isReleasable())
866	>	break;
867	>	else if (!queued)
868	>	queued = tryEnqueue(phase, node);
869	>	else {
870	>	try {
871	>	ForkJoinPool.managedBlock(node);
872	>	} catch (InterruptedException ie) {
873	>	node.wasInterrupted = true;
874	>	}
875	>	}
876	>	}
877	>	if (node != null) {
878	>	if (node.thread != null)
879	>	node.thread = null;
880	>	if (!node.interruptible && node.wasInterrupted)
881	>	Thread.currentThread().interrupt();
882	>	}
883	>	if (p == phase)
884	>	p = (int)(reconcileState() >>> PHASE_SHIFT);
885	>	if (p != phase)
886	>	releaseWaiters(phase);
887	>	return p;
888	>	}
889
890		/**
891		* Wait nodes for Treiber stack representing wait queue
#	Line 793 | Line 893 | public class Phaser {
893		static final class QNode implements ForkJoinPool.ManagedBlocker {
894		final Phaser phaser;
895		final int phase;
796	–	final long startTime;
797	–	final long nanos;
798	–	final boolean timed;
896		final boolean interruptible;
897	<	volatile boolean wasInterrupted = false;
897	>	final boolean timed;
898	>	boolean wasInterrupted;
899	>	long nanos;
900	>	long lastTime;
901		volatile Thread thread; // nulled to cancel wait
902		QNode next;
903
904		QNode(Phaser phaser, int phase, boolean interruptible,
905	<	boolean timed, long startTime, long nanos) {
905	>	boolean timed, long nanos) {
906		this.phaser = phaser;
907		this.phase = phase;
808	–	this.timed = timed;
908		this.interruptible = interruptible;
810	–	this.startTime = startTime;
909		this.nanos = nanos;
910	+	this.timed = timed;
911	+	this.lastTime = timed? System.nanoTime() : 0L;
912		thread = Thread.currentThread();
913		}
914
915		public boolean isReleasable() {
916	<	return (thread == null ||
917	<	phaser.getPhase() != phase ||
918	<	(interruptible && wasInterrupted) ||
919	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
916	>	Thread t = thread;
917	>	if (t != null) {
918	>	if (phaser.getPhase() != phase)
919	>	t = null;
920	>	else {
921	>	if (Thread.interrupted())
922	>	wasInterrupted = true;
923	>	if (interruptible && wasInterrupted)
924	>	t = null;
925	>	else if (timed) {
926	>	if (nanos > 0) {
927	>	long now = System.nanoTime();
928	>	nanos -= now - lastTime;
929	>	lastTime = now;
930	>	}
931	>	if (nanos <= 0)
932	>	t = null;
933	>	}
934	>	}
935	>	if (t != null)
936	>	return false;
937	>	thread = null;
938	>	}
939	>	return true;
940		}
941
942		public boolean block() {
943	<	if (Thread.interrupted()) {
944	<	wasInterrupted = true;
945	<	if (interruptible)
826	<	return true;
827	<	}
828	<	if (!timed)
943	>	if (isReleasable())
944	>	return true;
945	>	else if (!timed)
946		LockSupport.park(this);
947	<	else {
948	<	long waitTime = nanos - (System.nanoTime() - startTime);
832	<	if (waitTime <= 0)
833	<	return true;
834	<	LockSupport.parkNanos(this, waitTime);
835	<	}
947	>	else if (nanos > 0)
948	>	LockSupport.parkNanos(this, nanos);
949		return isReleasable();
950		}
951
#	Line 843 | Line 956 | public class Phaser {
956		LockSupport.unpark(t);
957		}
958		}
846	–
847	–	boolean doWait() {
848	–	if (thread != null) {
849	–	try {
850	–	ForkJoinPool.managedBlock(this);
851	–	} catch (InterruptedException ie) {
852	–	wasInterrupted = true; // can't currently happen
853	–	}
854	–	}
855	–	return wasInterrupted;
856	–	}
857	–	}
858	–
859	–	/**
860	–	* Removes and signals waiting threads from wait queue.
861	–	*/
862	–	private void releaseWaiters(int phase) {
863	–	AtomicReference<QNode> head = queueFor(phase);
864	–	QNode q;
865	–	while ((q = head.get()) != null) {
866	–	if (head.compareAndSet(q, q.next))
867	–	q.signal();
868	–	}
869	–	}
870	–
871	–	/**
872	–	* Tries to enqueue given node in the appropriate wait queue.
873	–	*
874	–	* @return true if successful
875	–	*/
876	–	private boolean tryEnqueue(QNode node) {
877	–	AtomicReference<QNode> head = queueFor(node.phase);
878	–	return head.compareAndSet(node.next = head.get(), node);
879	–	}
880	–
881	–	/**
882	–	* Enqueues node and waits unless aborted or signalled.
883	–	*
884	–	* @return current phase
885	–	*/
886	–	private int untimedWait(int phase) {
887	–	QNode node = null;
888	–	boolean queued = false;
889	–	boolean interrupted = false;
890	–	int p;
891	–	while ((p = getPhase()) == phase) {
892	–	if (Thread.interrupted())
893	–	interrupted = true;
894	–	else if (node == null)
895	–	node = new QNode(this, phase, false, false, 0, 0);
896	–	else if (!queued)
897	–	queued = tryEnqueue(node);
898	–	else if (node.doWait())
899	–	interrupted = true;
900	–	}
901	–	if (node != null)
902	–	node.thread = null;
903	–	releaseWaiters(phase);
904	–	if (interrupted)
905	–	Thread.currentThread().interrupt();
906	–	return p;
907	–	}
908	–
909	–	/**
910	–	* Interruptible version
911	–	* @return current phase
912	–	*/
913	–	private int interruptibleWait(int phase) throws InterruptedException {
914	–	QNode node = null;
915	–	boolean queued = false;
916	–	boolean interrupted = false;
917	–	int p;
918	–	while ((p = getPhase()) == phase && !interrupted) {
919	–	if (Thread.interrupted())
920	–	interrupted = true;
921	–	else if (node == null)
922	–	node = new QNode(this, phase, true, false, 0, 0);
923	–	else if (!queued)
924	–	queued = tryEnqueue(node);
925	–	else if (node.doWait())
926	–	interrupted = true;
927	–	}
928	–	if (node != null)
929	–	node.thread = null;
930	–	if (p != phase || (p = getPhase()) != phase)
931	–	releaseWaiters(phase);
932	–	if (interrupted)
933	–	throw new InterruptedException();
934	–	return p;
935	–	}
936	–
937	–	/**
938	–	* Timeout version.
939	–	* @return current phase
940	–	*/
941	–	private int timedWait(int phase, long nanos)
942	–	throws InterruptedException, TimeoutException {
943	–	long startTime = System.nanoTime();
944	–	QNode node = null;
945	–	boolean queued = false;
946	–	boolean interrupted = false;
947	–	int p;
948	–	while ((p = getPhase()) == phase && !interrupted) {
949	–	if (Thread.interrupted())
950	–	interrupted = true;
951	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
952	–	break;
953	–	else if (node == null)
954	–	node = new QNode(this, phase, true, true, startTime, nanos);
955	–	else if (!queued)
956	–	queued = tryEnqueue(node);
957	–	else if (node.doWait())
958	–	interrupted = true;
959	–	}
960	–	if (node != null)
961	–	node.thread = null;
962	–	if (p != phase || (p = getPhase()) != phase)
963	–	releaseWaiters(phase);
964	–	if (interrupted)
965	–	throw new InterruptedException();
966	–	if (p == phase)
967	–	throw new TimeoutException();
968	–	return p;
959		}
960
961		// Unsafe mechanics
#	Line 974 | Line 964 | public class Phaser {
964		private static final long stateOffset =
965		objectFieldOffset("state", Phaser.class);
966
977	–	private final boolean casState(long cmp, long val) {
978	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
979	–	}
980	–
967		private static long objectFieldOffset(String field, Class<?> klazz) {
968		try {
969		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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